Lubricating oil refining process



April 5, 1938-. c. F. TEARS LUBRICATING OIL REFINING PROCESS Filed Feb. 27, 1936 Patented Apr. 5, 1938 UNITED STATES LUBRICATING OIL REFINING PROCESS Claude F. Tears, Warren, Pa., assigner to The Petroleum Processes Corporation,

Wichita,

Kans., a corporation of Kansas Application February 27, 1936, Serial No, 65,082

4 Claims.

This invention relates to the refining of lubricating oils, particularly oils of the residual type, such as steam refined stock or long residuum or heavy distillate oils in which wax of the so-called amorphous type predominates.

Particular objects of the invention are to effect economies in operation and materials, to reduce plant equipment and hence necessary plant investment, to reduce the time required for rening and to eliminate the need for certain straining or finishing operations.

Other objects and the novel features of the process are set forth or will appear in the course of the following specification.

The drawing accompanying and forming par of the specification illustrates by way of a flow diagram one method of practicing the invention, but it is to be understood that changes and modifications may be made all within the true spirit and broad scope of the invention.

Specifically, the invention comprises the dewaxing and partial decolorization of oils combined with a propane or equivalent filtration for final decolorization to finished lubricating oils.

In conventional refinery operations, it is universal practice to decolorize or to at least partially decolorize or otherwise treat before dewaxing residual or heavy distillate stock. In more recently developed dewaxing processes, it is likewise customary to decolorize or otherwise treat the oil to be dewaxed.

In the co-pending C. F. Tears Patent 2,049,277 of July 28, 1936, a method of dewaxing and partially decolcrizing residual stocks without preliminary treatment is disclosed and in the copending C. F. Tears Patent 2,057,802 of Jan. l2, 1937, there is disclosed a method of decolorizing lubricating oil with the oil in solution in a normally gaseous liquefied hydrocarbon, such as propane.

The present invention is based on the discovery that these two methods may be modified and combined to effect marked economies and advantages in lubricating oil refining.

In the flow diagram, the rst phase of operations, involving the dewaxing and partially decolorizing is generally similar to the disclosure in Patent 2,049,277.

The charging stock, which may be an untreated and undecolorized residual steam refined stock, is pumped from storage tank l, by pump 2, to a mixer 3, where it is combined with a normally gaseous liquefied hydrocarbon solvent, such as propane delivered from storage tank 4, by pump 5.

The temperature of the mixture of oil and. solvent is raised by heater ii, to effect complete solution of the oil in the solvent and the mixture is then reduced in temperature by passage through cooler 1, to remove the added heat. A back pressure valve is indicated at 8, for holding the mixer, heater and cooler under sufficient pressure to maintain the solvent in the liquid state.

The solution of oil in propane or equivalent solvent is charged to the settler 9, which may be filled with the solution up to about of its full capacity. In a 10,000 gallon settler, the total charge might be 8,000 gallons, consisting of 2,000 gallons of oil and 6,000 gallonsof propane, or an oil to solvent ratio of 1 to 3. lWhen the 8,000 gallons is charged, the charging pumps are shut down and the settler is slowly vented to the compressor suction line l, through line Il, under control of valve i2. This evaporation of solvent serves to chill the mixture. 20

As the volume of the mixture is reduced by evaporation of the liquefied normally gaseous solvent, which for convenience of further description may be termed propane, more of such liqueed solvent is added by pump 5, from storage tank 4, sufficient to keep the level of liquid up to approximately the 80% level. This venting and replacement of propane may be continued as described until the pressure in the settler reaches about 30 lbs. per square inch, at which time the propane being evaporated may then be replaced by cold propane drawn from the cold propane tank i3.

Cold propane for storage in tank I3 is obtained in the illustration by expanding partially cooled liquid propane from exchanger i4, into the tank through line l5, from the propane storage tank 4, under control of an expansion valve I6. Propane Vapor from this local refrigerating operation passes to the compressor suction line i0 through a line I'l.

The compression system is shown as consisting of a compressor I8, and a connected condenser and cooler i9. Propane vapor entering the compressor through suction line i0 is compressed 45 to a sufficiently high pressure to permit condensation of the vapor in the condenser by cooling water at such temperature as is available. Normal operation with cooling Water temperatures usually available, requires a compression discharge pressure of about lbs. to 250 lbs. per square inch.

When the pressure on the settler has been reduced to atmospheric pressure, the mixture in the settler will be at a temperature of approx- 55 imately 40 F. and since the original volume of the mixture has been maintained by the addition of warm and cold prop'ane, the solution ratio has remained approximately the same as the original ratio given as 1 to 3. The warm and the cold propane, in the illustration, are introduced through the line 20, extending to the bottom of the settler. The introduction at this point, together with the agitation resulting from the boiling off of the propane vapor keeps the mixture in a constant state of agitation and in a substantially uniform mixture of solid wax, solid or semi-solid color constituents and oil in solution in cold propane. 'This mixture is then ready to prepare for the settling to separate the wax and the color constituents.

While the settler is being vented to atmospheric pressure, the cold propane tank I3 is also being vented to atmospheric pressure, to the compressor suction line, through line I1, so the propane in tank I3 is at approximately the same temperature as the contents of the settler. I'he settler may then be shut in by closing the vent valve I2. Cold propane from tank I3 is forced by pump 22, through line 2B, to the bottom of settler 9. The introduction of this cold propane into the bottom of the settler has the eiTect oi washing oil from the wax which starts to settle out as soon as the settler is shut in. The pump 22 may be continued in operation until the settler becomes completely lled and the pressure on the tank reaches approximately 75 lbs. per square inch. The settler is then completely shut in and the mixture permitted to settle quietly under pressure for a period usually of from 2 to 8 hours. Accidental heat losses are avoided by heavy insulation of the settler.

When the settler is completely full and ready for this settling, it contains, in the present illustration, a total of 10,000 gallons consisting of 2,000 gallons of charge and 8,000 gallons of propane, an oil to solvent ratio of 1 to 4.

As the wax and color constituents settle out of the mixture, the location of the top of the heavy layer can be found by following down with the swing line 24, which, as disclosed in Patent 2,049,- 277, carries a sample line arranged to withdraw a sample at the level of the lower, open end of the swing line. When the top of the heavy layer, as may be determined in this fashion, ceases to drop further in the settler, the mixture may be considered as completely settled and ready for removal of the supernatant oil solution layer.

In this completely settled condition, the solid and semi-solid constituents of the mixture have settled to the bottom of the settler and displaced, so far as possible, the solution of oil in propane. Under these conditions, the lower layer is made up of approximately 1 part propane and 1 part wax and color constituents. If the content of these constituents in the original charge was 15% for example, the heavy layer would then contain 300 gallons of the heavier constituents and 300 gallons of propane. The propane in the lower layer also carries with it some oil in solution, so it is usually advantageous to permit the settling to continue until the proportion of propane in the lower layer is as low as possibl-e. Complete settling of this kind in actual practice may be obtained in from, to 6 hours. When the settling is complete, there is practically a complete separation of solid and semi-solid constituents from the upper layer, but as pointed out, the lower layer will contain some oil in solution in the propane content in this layer. This separation however has been found to be as good or better than can be obtained by centrifuge operation and the yields of oil obtained from the operation are as good or better than can be obtained by centrifuge operation.

In the example under consideration, when the lower layer has settled to a propane to solid material ratio of 1 to l, the amount of .propane in such layer is 300 gallons. This leaves a balance of '7,700 gallons which has been displaced into the top or oil layei which is then holding in solution 1,700 gallons of dewaxed and partially decolorized oil, an oil to propane ratio of approximately 1 to 4.53 in the upper layer.

During the settling stage, the swing line 24, as described above, is moved down until its inlet is right at the top of the bottom layer at the end of the settling period. Valve 25 may then be opened and the oil layer be pumped out of the settler by means of pump 26, through line 2l, and by way of exchanger I4, and heater 2B, to one or the other of the percolation filters 39, 40.

In the exchanger I4, the cold oil solution from the settler exchanges heat with liquid propane being charged to the cold propane tank I3, through line I5, from storage tank 1I. In the heater 28, the dewaxed and partially decolorized propane-oil solution which has picked up heat in the exchanger I4, is brought up to a temperature of from about 110 F. to 140 F. (the optimum decolorizing temperature) by steam, hot oil or any other convenient heating medium and is then ready for the final decolorizing.

After the oil layer has been completely removed, the settler is shut in again by closing valve 25, and hot oil is circulated through the heating coils 29, in the bottom of the settler to heat the mixture remaining in the settler. This heating is continu-ed until pressure on the settler is within the range of 200 to 250 lbs. per square inch. Such pressure is sucient and is utilized to expel the contents of the settler, in a preheated condition, through line 30, and valve 3l, directly to the wax stabilizer 32, which latter operates at the same pressure as the discharge of the compressor. The wax stabilizer is shown as heated by coil 33, in the bottom of the same which serves to distill off most of the propane in the heavy layer. The propane vapor from this wax stabilizer passes off through the vapor line 34, directly to the propane condenser I9, where it is condensed and returned in liquid form to the propane storage tank 4.

From the bottom of the stabilizer, the partially denuded waxy layer material containing the color constituents removed from the oil, passes, under the pressure of the stabilizer, directly to the wax stripper 35, which operates at the pressure of the suction side of the compressor, being connected with the compressor suction line I0, through line 36. This wax stripper is shown as heated by coil 31, to drive off the remaining traces of propane as vapor to the compressor suction line, which vapor is compressed, condensed and returned to the propane storage tank. The denuded waxy layer material passes out through cooler 38, to wax storage.

The two percolation lters 39, and 40 are charged with any desired adsorbent decolorizing agent, such as 30/60 or 60/90 mesh fullers earth, which ordinarily is the most easily reactivated available material. The hoppers for charging the adsorbent decolorizing medium are indicated at 4I, 42. These filters are of the pressure type required for handling the propane-oil solution in the liquid state and may be connected as indicated for series, or parallel, or alternate operation.

In a preferred method, the heated dewaxed and partially decolorized propane-oil solution is entered in the top of filter 39, through line 43, passes down through the bed of fullers earth and out through line d, to the oil stabilizer 45, in the preheated condition provided by the heater 28. This flow may be continued until the color of the stream from the lter reaches a predetermined color standard. At this stage, the color of the iinished oil may be as dark as desired, but the adsorbent will not be completely exhausted as a decolorizing agent. The stream from the bottom of the first filter may then be diverted to the top of iilter 40, which contains a fresh charge of fullers earth, this change being accomplished by manipulation of the valved manifolding 5l, 62, indicated at the bottom and top of these two filters. This flow is continued through filters 39, and 40, in series, with the decolorized oil solution passing out at the bottom of the second filter to the oil stabilizer 45, until the fullers earth in the first iilter is completely exhausted. When this occurs, the iirst iilter is cut out of service, for replacement of the decolorizing medium. The flow from the propane-oil solution heater 28, may then be sent directly to the top of the second filter 40.

The exhausted fullers earth in filter 39, preferably is first washed with clean liquid propane to remove oil held in the bed of filter material. This washing propane in the illustration, is pumped from the propane storage tank 4, by a pump 52, through line 53, into the bottom of the lter and flows up through the filter bed and into the propane-oil solution stream entering the top of iilter 40, the manifold valve 63, at the top being closed at this time and valves 64, 65, 55, being open. The washing propane can be heated, if desired, in this course of flow by heating coil 54, in the filter being Washer.

When the oil is washed out of the exhausted fullers earth in lter 39, the flow of propane is stopped and the whole contents of the lter is further heated, by heating coil 54, to vaporize and drive off the propane from the fullers earth. 'Ihe propane vapor thus released passes directly to the propane condenser upon opening valves 46 and 55, in line 81, the valve 55, leading from this line to the suction side of the compressor being closed at the time. 'When all the propane that can be vaporized at the pressure on the condenser, has passed off, valve 55 is closed and valve 56, is opened, so the vapor will pass into the suction side of the compressor. This action lowers the pressure and completely vaporizes any remaining propane in the filter, into the suction side of the compressor, for recovery by compression and condensation.

The dumping manhead cover 5l, at the bottom of the filter may then be removed and the exhausted fullers earth released into hopper 58, from which it may be delivered to a conventional roasting retort for reactivation. This filter may then be charged with new or reactivated fullers earth ready for use again.

Washing the exhausted fullers earth with fresh propane completely removes oil retained by the adsorbent and this propane is then completely removed first by heating and discharging to the pressure side of the compressor and then by subjecting it to the suction of the coinpresser. This leaves the exhausted fullers earth so it will flow freely and can be easily handled.

Furthermore, this procedure avoids losses of solvent and oil with the exhausted fullers earth, such as usually resulting in conventional decolorizing lter operation.

When the color of the stream from the second lter 40, has reached the predetermined color standard7 the flow is changed, by the valved manifolds at 6l, 62, from the bottom of filter 40, back to the top of the fresh charged filter 39, and from the bottom of this filter, through 44, to the oil stabilizer 45. When' the adsorbent in filter 40 becomes exhausted, this filter may be cut out and the material be cleaned and removed as described for the first filter. y

The oil stabilizer 45, and the oil stripper 59, may be operated in the same manner as described for the wax stabilizer and stripper 32, 35, the stabilizer distilling off the major portion of the propane under high pressure and the stripper removing the last traces of propane, under heat at low pressure. The dewaxed and decolorized oil is run down from the oil stripper 59, through cooler 60, to storage.

In a commercial installation of thev process a multiplicity of settlers are usually provided and at least three pressure filters. This enables the settlers to be operated on a staggered schedule, assuring continuous flow of oil solution to the lters, as one settler Will be ready for oil removal by the time all oil is removed from a settler ahead of it. The use of three or more filters allows for one being out of service as for cleaning and charging, while the other two are in series operation.

It will be obvious that the combining of the dewaxing and partial decolorizing with the final decolorizing operation, results in very definite economies and advantages. v

The oil which is charged to the filters is already partially decolorized, so that greatly increased yields of finished oil per ton of fullers earth can be obtained. This materially reduces the cost of operations as the decoilorizing medium is the most expensiveitem in decolorization processes.

In Pennsylvania refineries, the universal conventional p-ractice is to decolorize steam refined stock before dewaxing. The color of conventional Pennsylvania 150 viscosity 210 F.) steam refined stock is 61/2 N. P. A. in 5% solution naphtha. The color of the partially decolorized oil from the dewaxing and partially decolorized stage of this process is 4%, to 4 N. P. A. in 5% solution naphtha. This is an important reductionin total color to be removed by filtration and it is obtained at no cost, in the dewaxing operan tion.

:Decolorizing filtration of oil in propane solution under the conditions described, results in an increase in yield of finished oil per ton of fullers earth of from 200% to 400%. This, in conjunction with the saving considered in the preceding paragraph, serves to reduce the cost of the decolorizing medium to a mere fraction of the costs under conventional practice.

The conventional method of filtering steam Cil llO

Petrolatum under normal market conditions, v

has a value of. only 21/2 to 31/2 per gallon for use as fuel oil or as an ordinary cracking stock. In many plants, the cost of decolorizing this product is as much as its total value as fuel oil. The petrolatum produced from the process described herein is a dark colored product, but it still retains its value as fuel oil or cracking stock, so any money expended for decolorizing it, would be wasted. The present process avoids the cost of decolorizing the petrolatum and also increases the finished decolorized cil yield per ton of decolorizing medium, by the volume of petrolatum removed in the dewaxing stage.

It is the generally universal practice in all reneries to handle the dewaxing and the decolorizing ltration in separate departments, with separate equipment and different operating crews. In the present process, all operations are combined and carried on in the same installation and by the same crew. The solvent supply and recovery systems, compressor, condenser, heat exchanger and other members are common to both stages of operations. In the dewaxing stage, the oil is put into propane solution and heat is later applied to effect removal of the propane. These operations are connected portions of both the dewaxing and the decolorizing stages of the process. Solvent losses may be charged to the dewaxing stage and all solvent is recovered from the filtration stage. In conventional iilter operation, the cost of the decolorizing medium represents from 50% to 75% of the total oost, the balance of the cost being-for steam, labor, etc., and for solvent and oil losses. In this process, the cost ofA decolorization is reduced to practically the bare cost of the decolorizing medium and the yield of finished oil per ton of decolorizing medium is greatly increased over the conventional methods.

The possible rate of flow of oil per ton of decolorizing medium or per unit of. cross-sectional area of the iilter, through the filtration stage of this process is approximately 21/2 times the possible rate's in conventional practice, so the size of necessary equipment is greatly reduced and the amounts of solvent and decolorizing medium required in the system are much smaller.

In conventional lter operation in naphtha solution, relatively high temperatures are required to distill off the naphtha. This increases the color of the iiltered oil and makes it necessary to strain the oil. This straining consists in passing the stripped oil through a second smaller bed of fullers earth. In the process herein described, the temperature required to remove the propane is not high enough to throw oii the color of the oil and as a consequence, the necessity for straining is avoided.

The foregoing advantages and distinctions are the direct result of combining the dewaxing and decolorizing stages in a way such that favorable conditions in one are taken advantage of in the other stage and it will be realized that certain or all of. these advantages may be attained, with modification of the structure and operation in various ways. It is possible, for example, that a Contact method of decolorizing, such as covered in the co-pending C. F. Tears patent application, Ser. 727,497 may be substituted for the percolation decolorization illustrated. Many other changes are possible within the scope of the invention, as will be apparent from the following claims and in View of such scope, it should be understood that the terms employed herein, have been used in a descriptive rather than in a limiting sense, except where a limiting intent clearly appears or possibly may be required by state of the prior art.

By combining the dewaxing and decolorizingV operations as disclosed, the same solvent can be employed and without any intermediate solvent recovery operations and the heat which is added to obtain optimum results in the decolorizing stage can be later employed for stripping the solvent in the solvent recovery unit, which is common to both stages. Thus the cost of iinal decolorizing operations can be kept down to practically the cost of the decolorizing agent.

The amount oi oil to be decolorized is reduced by the amount of wax and color bearing compounds removed in the dewaxing stage. For instance, in conventional refinery practice when running Pennsylvania steam rened stock, the total steam refined stock is iirst decolorized and then dewaxed. When making conventional 25 pour bright stock, the wax or petrolatum yield ls approximately 12 to 20%. In the present prosess this 12 to 20% content of, wax need not be decolorized because of the dewaxing of the untreated stock.

What is claimed is:

1. The herein disclosed process of dewaxing and decolorizing a previously untreated nondewaxed and undecolorized residual lubricating oil stock, which comprises mixing an untreated waxcontaining and color bearing undecolorlzed residual lubricating oil stool: in normally gaseous liquefied hydrocarbon solvent under pressure, under temperature and pressure conditions to eiect solution of said residual oil stock in said solvent, chilling said mixture to below wax solidliication temperature, separating the wax and an accompanying portion of color bearing components in a combined state from said mixture while maintaining the chilled mixture under pressure above the normal vapor pressure of the solvent at the temperature of the chilled mixture, heating the dewaxed and partially decolorized oil solvent solution under pressure to a temperature substantially above atmospheric temperature, subjecting said heated, dewaxed and partially decolorized oil solvent solution to the decolorizing action of adsorbent decolorizing medium and filtration, under pressure sufcient to maintain said solvent in the liquid state and then passing said then dewaxed and decolorized oil from said decolorizing iiltration stage while still in the same solvent solution and still under pressure, to a separation zone and there separating the solvent from the dewaxed and decolorized oil.

2. The process of claim 1 with the added steps of removing the combined wax and color bearing components from the rst separating stage, separating the solvent from the combined wax and color bearing components and collecting the solvent separated from the dewaxed and decolorized oil and the solventseparated from the combined wax and color bearing components in a common recovery system.

3. A process as in claim l, in which the dewaxed and partially decolorized oil solvent solution is heated within the temperature range of 118 F. to 140 F. before the subjecting of the same to the decolorizing action of adsorbent decolorizing medium and ltration.

4. A process as in claim l, in which the normally gaseous liquefied hydrocarbon solvent is propane.

CLAUDE F. TEARS. 

